Polyarylenes exhibit some outstanding performance properties, including exceptionally high strength, stiffness, hardness, scratch resistance and dimensional stability. Kinked rigid rod polyarylenes exhibit further a good processability and fusibility, in substantial progress with unkinked rigid-rod polyarylenes.
Generally speaking, the merits of polyarylenes have been known for several years. To this point, the INTERNET website of SOLVAY ADVANCED POLYMERS currently mentions, op. cit.: “Make a Fire Without the Smoke. Studies show that Primospire™ SRPs [=polyphenylenes, generally speaking] may offer excellent performance for ablative insulation. With zero toxic emissions (CO2 and H2O are the byproducts) and superior mechanicals pre- and post-char formation, Primospire SRPs are lightweight alternatives to ceramic and metal insulative materials.”
Also generally speaking, the introduction of a scientific publication entitled “Continuous foam extrusion of rigid-rod polyphenylenes”, Journal of Cellular Plastics, 41(1), pages 29-39, cites as potential applications of Parmax® SRPs materials (now marketed as Primospire SRPs), fire resistant structures, additives to enhance the properties of polymers, high performance films and abrasion resistance coatings. Then, this publication addresses a new method for making foams, for which experiments made using an experimental specific kinked rigid-rod polyphenylene supplied by Mississipi Polymer Technologies, namely Parmax® 1500 (still now at the developmental stage, and available from SOLVAY ADVANCED POLYMERS as PRIMOSPIRE™ PR-250 polyphenylene). This publication does neither describe the use of PRIMOSPIRE™ PR-250 and type specifically as fire-stabilizer, or for making films or coatings, nor does it suggest any merit that would result in the use of this specific type of polyarylene for the previously cited specific end uses.
Similarly, U.S. Pat. No. 5,886,130 describes and exemplifies (notably in example 5) certain kinked rigid-rod polyarylenes of the same type as PRIMOSPIRE™ PR-250, characterized by a high amount of kink-forming recurring units. The same patent describes and exemplifies (notably in example 11) certain other kinked rigid-rod polyarylenes characterized by a low amount of kink-forming recurring units, the only broadly commercially available representative of this class is PRIMOSPIRE™ PR-120 polymer (formerly, PARMAX® 1200). Among other possible applications of the kinked rigid-rod polyarylenes described in US'130, are fiber coatings, fibers, films and sheets. This publication does neither describe the use of a specific type of kinked rigid-rod polyarylene rich in kink-forming units specifically as fire-stabilizer, or for making films or coatings, nor does it suggest any merit that would result in the use of this specific type of polyarylene for the previously cited specific end uses.
Back to PRIMOSPIRE™ PR-120 polyarylene specifically. It is known that PRIMOSPIRE™ PR-120 polymer can be used as a inherently fire-resistant material and can further significantly improve the fire-resistance properties of other polymers. It is also known to use such Primospire™ PR-120 polyarylene, as base polymer on as additive to compositions based on other polymers, for the manufacture of certain ultra-thin shaped articles such as films and coatings, for which the fire-resistance is generally considered as a key property by the skilled in the art, because, despite of their thinness, said films and coatings represent generally the first effective barrier against a potentially external aggressive environment.
While PRIMOSPIRE™ PR-120 polyarylene does well provide the expected level of fire resistance in certain application, PRIMOSPIRE™ PR-120 polyarylene does not offer a level of fire resistance as high as needed in certain other more demanding applications, as those which may be found in aircraft and civil transportations. As an immediate result thereof and also since films and coatings made from PRIMOSPIRE™ PR-120 polyarylene are prone to various surface defects, there is still a strong need in fire-retarded applications for a material offering an increased fire-resistance when compared to the prior art polyarylenes, in particular PRIMOSPIRE™ PR-120 polyarylene, and which makes it then possible to make fire-retarded films and coatings exhibiting an increased fire resistance, and, desirably also, an improved surface aspect.